In current, state of the art magnetic tape recorders adapted for computer data storage, a read-while-write capability is an essential feature for providing virtually error free magnetically stored data. A read-while-write head assembly comprises a write element in-line with a read element, the gap of the read element being closely spaced to the gap of the write element, with the read element positioned downstream of the write element in the direction of tape motion. By continually reading "just recorded" data, the quality of the recorded data is immediately determinable at a time when the original data is still available in temporary storage in the recording system. The reproduced data is checked against the original data, and appropriate action, such as re-recording, may be taken in case of error.
Many modern tape recording systems require operation where writing and reading of the data occurs for either direction of tape travel. The streaming tape system where the recording is laid down on the tape in a serpentine pattern for alternate directions of tape travel is an example of such a bidirectional recording system. Incorporation of read-while-writing capability for bidirectional operation has traditionally necessitated a head assembly consisting of three heads: a first write element adjacent to a read element which is adjacent to a second write element, or a first read element adjacent to a write element which is adjacent to a second read element. See, for example, U.S. Pat. No. 5,034,838 (Brock).
The quantity of data stored on a magnetic tape may be increased by increasing the number of data tracks on the tape, thereby decreasing the distance between the centerlines of adjacent tracks. Tape heads which are suitable for reading and writing on such tapes require a high level of precision in the alignment of the read and write elements in the head assembly. This may be achieved by minimizing the distance between each read element and its respective write element. The problem of aligning the read and write elements may also be simplified by eliminating one of the three heads, although, as in the case of the IBM 3480 system, this has traditionally eliminated the capability of bidirectional read-while-write.
Tape heads also suffer from the problem of head wear caused by the magnetic recording tape. Repeated passes of a tape over the tape head will, over time, wear away at the surface of the tape head, which can impair the performance of the head.
It would be desirable to have a tape head assembly which (1) minimizes head wear, (2) minimizes the distance between the read elements and their respective write elements by combining both elements into a single head assembly, (3) requires only a single pair of read and write elements per track (and not two reads and a write or two writes and a read) and (4) has bidirectional read-while-write capability.